The present invention relates generally to image generating systems, and more particularly to optics arrangements especially suitable for miniaturized image generating systems such as the miniaturized image generator disclosed in pending U.S. patent application Ser. No. 08/362,665 Attorney Docket Number DIS1P003 entitled ACTIVE MATRIX LIQUID CRYSTAL IMAGE GENERATOR filed Dec. 22, 1994.
One of the ongoing challenges facing the manufacture of miniature image generating systems is providing smaller and more durable systems. Miniature image generating systems which are small enough to be mounted onto a helmet or small enough to be supported by a pair of eyeglasses will find a wide variety of uses if they can provide adequate resolution and brightness in a small, low-power, and durable pack, age at a low cost. Conventional technologies such as CRTs are difficult to miniaturize and therefore do not hold much promise for further development in this field. Alternatively, new systems based on VLSI integrated circuits are currently being developed which provide much smaller spatial light modulators for use in a miniaturized image generating systems. However, one of the problems in this field is providing optics and illuminating arrangements which may be scaled down in coordination with the miniaturized spatial light modulator in order to provide an overall image generating system which is practical and compact enough to be mounted onto a helmet or supported by a pair of glasses. Pending U.S. patent application Ser. No. 08/362,234 Attorney Docket Number DIS1P005 entitled OPTICS ARRANGEMENTS INCLUDING LIGHT SOURCE ARRANGEMENTS FOR AN ACTIVE MATRIX LIQUID CRYSTAL IMAGE GENERATOR filed Dec. 22, 1994, discloses novel arrangements for providing various illumination and optics arrangements which address some of these problems and which may be incorporated into certain embodiments of the present invention.
Referring to FIG. 1A, a prior art miniature image generator system generally designated by reference numeral 10 will be described. System 10 includes a miniature CRT 12 which produces a desired image. A beam splitting cube 14 is positioned such that a first external face 16 of cube 14 is located adjacent to the light emitting surface of CRT 12. System 10 also includes an optical element 18 having a curved light reflecting surface 20 positioned adjacent to a second external face 22 of cube 14. As shown in FIG. 1A, this arrangement results in an overall system which allows a viewer to view the image produced by CRT 12 when the viewer's eye, indicated at 24, is positioned in front of a third external face 26 of cube 14.
In the above described arrangement, as indicated by line 28 in FIG. 1, a portion of the light emitted from CRT 12 into cube 14 is reflected toward optical element 18 by an internal beam splitting layer 30 positioned diagonally within cube 14. Curved light reflecting surface 20 of optical element 18 reflects this light back through cube 14 such that a portion of the light passes through beam splitting layer 30. This arrangement allows a viewer to view the image produced by CRT 12 when the viewer's eye is positioned in front of external cube face 26.
Alternatively, as shown in FIG. 1B wherein like components are designated by like reference numerals in FIGS. 1A and 1B, if cube 14 is a polarizer-analyzer beam splitting cube, hereinafter referred to as a polarizing beam splitting cube, internal layer 30 would be a polarizing beam splitting layer which directs light of one polarization, for example S-polarized light, from CRT 12 into optical element 18. For this arrangement, a quarter wave plate 32 is positioned between cube 14 and optical element 18. As described above, curved light reflecting surface 20 of optical element 18 reflects this light back through cube 14. However, for the polarizing beam splitting version, quarter wave plate 32 changes the polarization of the light directed into optical element 18 such that the light directed back into cube 14 by optical element 18 is the opposite polarization, in this example P-polarized light. This P-polarized light passes through polarizing beam splitting layer 30 allowing a viewer to view the image produced by CRT 12 when the viewer's eye is positioned in front of external cube face 26.
Although the above described prior art arrangements are functional, because a CRT is used to form the desired image, there are limitations in how far this arrangement can be scaled down. As will be seen hereinafter, the present invention provides a variety of novel optics arrangements which, when combined with miniaturized spatial light modulators in novel ways, are capable of providing compact miniaturized image generating systems that may be used to produce a direct view miniature display substantially smaller than the CRT based systems described above.